Capacitary estimates and the local behavior of solutions of nonlinear subelliptic equations

We establish sharp capacitary estimates for Carnot-Caratheodory rings associated to a system of vector fields of Hormander type. Such estimates are instrumental to the study of the local behavior of singular solutions of a wide class of nonlinear subelliptic equations. One of the main results is a generalization of fundamental estimates obtained independently by Sanchez-Calle and Nagel, Stein and Wainger.